From 36d1f095a6a29dd11d5e2d9e189e5f60cf82d19e Mon Sep 17 00:00:00 2001
From: Stefan Behnel <scoder@users.berlios.de>
Date: Thu, 4 Mar 2010 22:56:20 +0100
Subject: [PATCH] removed code redundancy: do not generate
 ParallelAssignmentNode in parser at all, only in PostParse transform

---
 Cython/Compiler/ParseTreeTransforms.py | 25 ++++++++++++++++---------
 Cython/Compiler/Parsing.py             | 10 ++--------
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/Cython/Compiler/ParseTreeTransforms.py b/Cython/Compiler/ParseTreeTransforms.py
index e58a1784..0d6aa2b9 100644
--- a/Cython/Compiler/ParseTreeTransforms.py
+++ b/Cython/Compiler/ParseTreeTransforms.py
@@ -242,18 +242,25 @@ class PostParse(CythonTransform):
             self.context.nonfatal_error(e)
             return None
 
-    def visit_ParallelAssignmentNode(self, node):
+    # support for parallel assignments (a,b = b,a) by splitting them
+    # into separate assignments that are executed rhs-first
+
+    def visit_SingleAssignmentNode(self, node):
+        self.visitchildren(node)
+        return self._visit_assignment_node(node, [node.lhs, node.rhs])
+
+    def visit_CascadedAssignmentNode(self, node):
+        self.visitchildren(node)
+        return self._visit_assignment_node(node, node.lhs_list + [node.rhs])
+
+    def _visit_assignment_node(self, node, expr_list):
         """Flatten parallel assignments into separate single
         assignments or cascaded assignments.
         """
-        self.visitchildren(node)
-        expr_list = []
-        for assign_node in node.stats:
-            if isinstance(assign_node, Nodes.CascadedAssignmentNode):
-                expr_list.extend(assign_node.lhs_list)
-            else:
-                expr_list.append(assign_node.lhs)
-            expr_list.append(assign_node.rhs)
+        if sum([ 1 for expr in expr_list if expr.is_sequence_constructor ]) < 2:
+            # no parallel assignments => nothing to do
+            return node
+
         expr_list_list = []
         flatten_parallel_assignments(expr_list, expr_list_list)
         nodes = []
diff --git a/Cython/Compiler/Parsing.py b/Cython/Compiler/Parsing.py
index 2cc046f0..c97d700c 100644
--- a/Cython/Compiler/Parsing.py
+++ b/Cython/Compiler/Parsing.py
@@ -920,18 +920,12 @@ def p_expression_or_assignment(s):
 
     rhs = expr_list[-1]
     if len(expr_list) == 2:
-        node = Nodes.SingleAssignmentNode(rhs.pos, 
+        return Nodes.SingleAssignmentNode(rhs.pos, 
             lhs = expr_list[0], rhs = rhs)
     else:
-        node = Nodes.CascadedAssignmentNode(rhs.pos,
+        return Nodes.CascadedAssignmentNode(rhs.pos,
             lhs_list = expr_list[:-1], rhs = rhs)
 
-    if sum([ 1 for expr in expr_list if expr.is_sequence_constructor ]) > 1:
-        # at least one parallel assignment
-        return Nodes.ParallelAssignmentNode(node.pos, stats = [node])
-    else:
-        return node
-
 def p_print_statement(s):
     # s.sy == 'print'
     pos = s.position()
-- 
2.26.2